Lignin modified furyl polyester material as well as preparation method and application thereof

Abstract

The invention discloses a lignin modified furyl polyester material as well as a preparation method and application of the lignin modified furyl polyester material, and relates to the technical field of polymer composite materials. The structural formula of the modified furyl polyester material comprises a structural unit derived from a lignin compound and a structural unit derived from furyl polyester; the structural unit derived from the lignin compound accounts for 0.5 wt%-12wt% of the structural unit derived from the furyl polyester, and preferably, the structural unit derived from the lignin compound accounts for 1.5 wt%-12wt% of the structural unit derived from the furyl polyester. The lignin modified furyl polyester material is designed by taking furyl polyester and modified lignin as basic materials. The modified lignin is used as a monomer raw material to be added into a low-molecular-weight furyl polyester melt polycondensation reaction, then a chain extender is added to react with the lignin modified furyl polyester to form carbamate bonds, and crosslinking and reinforcing effects are achieved. The elastic modulus of the modified furyl polyester material is increased, and the first-circle recovery rate and the elastic property are improved. In addition, by utilizing the inherent characteristics of lignin, the modified polyester material shows excellent ultraviolet shielding performance. The mechanical property of the furyl polyester material is improved, the traditional dependence on high-molecular-weight polyester is broken through, and a new example is provided for value-added utilization of lignin in sustainable bio-based polyester.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and more specifically, to a lignin-modified furan-based polyester material, its preparation method, and its application. Background Technology

[0002] The scarcity of fossil resources and escalating plastic pollution have spurred demand for renewable bio-based polymer materials, thereby reducing greenhouse gas emissions and promoting carbon neutrality and sustainable development. 2,5-Furandicarboxylic acid (FDCA), the only aromatic monomer among the 12 most representative bio-derived chemicals selected by the U.S. Department of Energy in 2004, has attracted increasing attention due to its chemical stability and biodegradability. FDCA is generally derived from lignocellulose or fructose through a tandem conversion process. Against the backdrop of a global push to ban plastics, FDCA has become an ideal alternative to terephthalic acid (TPA) in the synthesis of bio-based polyester materials.

[0003] The mechanical properties of polyesters are directly related to their molecular weight. Typically, a molecular weight exceeding 40,000 Da is required to ensure excellent mechanical properties. However, oligomer formation is a common problem in distribution polymerization, and the preparation of high molecular weight furanyl polyesters remains a challenge, requiring strict control of reaction conditions, prolonged high-temperature reactions, and considerable energy consumption.

[0004] Lignin is a three-dimensional biopolymer rich in plant cell walls and is one of the most abundant aromatic biomass resources. Structurally, lignin is a hyperbranched macromolecule with abundant functional groups such as hydroxyl and carboxyl groups. Lignin possesses excellent UV shielding ability, effective photothermal properties, and low cost. Therefore, lignin shows great potential as an excellent natural aromatic raw material for polyester modification. However, due to lignin's high steric hindrance and low reactivity, most lignin-modified polyesters exhibit poor mechanical properties. Furthermore, lignin is incompatible with polyesters, resulting in limited addition amounts and impacting mechanical properties. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a lignin-modified furan-based polyester material, its preparation method, and its applications. This invention prepares furan-based polyesters of a certain molecular weight using appropriate technology and a catalyst system with specific selectivity and activity. Utilizing the characteristic that lignin reacts chemically with formaldehyde when heated under alkaline conditions, hydroxymethyl groups are introduced into the ortho position of the aromatic ring, effectively increasing the number of hydroxyl groups in the lignin and their activity in the polyester reaction. The alcohol hydroxyl groups in the modified lignin can participate in the melt polycondensation of the furan-based polyester prepolymer. Subsequently, by adding the chain extender diisocyanate, a reaction can be formed with the phenolic hydroxyl groups in the modified lignin to form urethane bonds, achieving graft crosslinking of the furan-based polyester and further improving its toughness. Furthermore, utilizing the inherent properties of lignin, the modified polyester material exhibits excellent ultraviolet shielding performance.

[0006] One of the objectives of this invention is to provide a lignin-modified furan-based polyester material.

[0007] The lignin-modified furan-based polyester material of the present invention comprises structural units derived from lignin compounds and structural units derived from furan-based polyesters.

[0008] The structural unit derived from lignin compounds is 0.5wt%-12wt% of the structural unit derived from furanyl polyester, preferably 1.5wt%-12wt%.

[0009] A second objective of this invention is to provide a method for preparing lignin-modified furan-based polyester materials as described in one objective of this invention.

[0010] The method for preparing the lignin-modified furan-based polyester material of the present invention includes:

[0011] Hydroxymethyl modified lignin is prepared by heating lignin compounds with formaldehyde under alkaline conditions, followed by melt polycondensation with furan-based polyester prepolymer obtained by esterification, and then crosslinking by grafting with a chain extender to obtain the modified furan-based polyester material.

[0012] In a preferred embodiment of the present invention, the method includes:

[0013] (1) Preparation of hydroxymethyl modified lignin:

[0014] The hydroxymethyl modified lignin was obtained by stirring lignin compounds, formaldehyde solution and alkaline compound evenly and then heating to react, followed by washing and drying.

[0015] (2) Preparation of furanyl polyester prepolymer:

[0016] Under a protective gas atmosphere, 2,5-furandicarboxylic acid compound, aliphatic diol, aromatic dicarboxylic acid compound, and aliphatic dicarboxylic acid are subjected to esterification reaction under the catalysis of a first catalyst and a second catalyst to obtain the furan-based polyester prepolymer.

[0017] (3) Melt polycondensation:

[0018] The hydroxymethyl modified lignin is added to the furanyl polyester prepolymer for pre-condensation and final condensation reactions to obtain a pre-modified furanyl polyester material.

[0019] (4) Grafting crosslinking:

[0020] The pre-modified furan-based polyester material is dissolved in an organic solvent, and a chain extender and a third catalyst are added to carry out a grafting and crosslinking reaction. After curing and drying, the modified furan-based polyester material is obtained.

[0021] In a preferred embodiment of the present invention:

[0022] In step (1):

[0023] The concentration of the formaldehyde solution is 30-40%; and / or,

[0024] The weight ratio of the lignin compound to formaldehyde is (4-10):1, preferably (5-8):1; and / or,

[0025] The weight ratio of the lignin compound to the alkaline compound is (20-30):1, preferably (22-26):1.

[0026] In a preferred embodiment of the present invention:

[0027] In step (2):

[0028] The molar ratio of the aliphatic diol to the total molar ratio of the 2,5-furandicarboxylic acid compound, the aromatic dicarboxylic acid compound, and the aliphatic dicarboxylic acid is (1.0–4):1, preferably (1.2–2):1; and / or,

[0029] The molar ratio of the aliphatic dicarboxylic acid to the total molar ratio of the 2,5-furandicarboxylic acid compound and the aromatic dicarboxylic acid compound is (0.5–2):1, preferably (0.7–1.5):1; and / or,

[0030] The molar ratio of the 2,5-furandicarboxylic acid compound to the aromatic dicarboxylic acid compound is 1:(0.4–1.8), preferably 1:(0.4–1.2), more preferably 1:(0.8–1.2); and / or,

[0031] The first catalyst is 0.05–1 wt% of an aliphatic dicarboxylic acid, preferably 0.1–0.8 wt%, more preferably 0.2–0.5 wt%; and / or,

[0032] The second catalyst is 0.05 to 2 wt% of the weight of an aliphatic dicarboxylic acid, preferably 0.1 to 1 wt%, more preferably 0.1 to 0.4 wt%.

[0033] In a preferred embodiment of the present invention:

[0034] In step (3):

[0035] The hydroxymethyl modified lignin is 1 wt% to 25 wt% of the total weight of 2,5-furandicarboxylic acid compound and aliphatic diol, preferably 4 wt% to 15 wt%.

[0036] In a preferred embodiment of the present invention:

[0037] In step (4):

[0038] The concentration of the pre-modified furan-based polyester material dissolved in an organic solvent is 0.01–1 g / mL, preferably 0.05–0.5 g / mL; and / or,

[0039] The chain extender is 0.2–2.5 wt% of the weight of the pre-modified furan-based polyester material, preferably 0.3–2.5 wt%; and / or,

[0040] The third catalyst is 0.01 to 1 wt% of the weight of the pre-modified furan-based polyester material, preferably 0.1 to 0.5 wt%.

[0041] In a preferred embodiment of the present invention:

[0042] In step (1):

[0043] The lignin compound may be a commonly used lignin compound in the art, preferably at least one of alkali lignin, enzymatically hydrolyzed lignin, and high-boiling-point alcohol lignin; and / or,

[0044] The alkaline compound is an alkali metal hydroxide, preferably sodium hydroxide and / or potassium hydroxide.

[0045] In a preferred embodiment of the present invention:

[0046] In step (2):

[0047] The 2,5-furandicarboxylic acid compound is at least one selected from 2,5-furandicarboxylic acid, dimethyl 2,5-furandicarboxylate, and diethyl 2,5-furandicarboxylate; and / or,

[0048] The aliphatic diol is at least one selected from butanediol, hexanediol, decanediol, octanediol, nonanediol, and pentanediol, preferably butanediol; and / or,

[0049] The aromatic dicarboxylic acid compound is at least one selected from terephthalic acid, terephthalate, isophthalic acid, and isophthalate; and / or...

[0050] The aliphatic dicarboxylic acid is at least one selected from adipic acid, succinic acid, sebacic acid, octanoic acid, azelaic acid, tridecanoic acid, and glutaric acid, preferably adipic acid and / or succinic acid; and / or,

[0051] The first catalyst is at least one of an organotitanium catalyst, an organotin catalyst, and an organoantimony catalyst; preferably, the organotitanium catalyst is at least one of tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, and titanium glycolate, and / or, the organotin catalyst is at least one of dibutyltin oxide, butylstanonic acid, dibutyltin oxide, diethyldibutyltin, dioctyltin oxide, monobutyldiisooctanoate, and stannous octanoate, and / or, the organoantimony catalyst is at least one of antimony trioxide, antimony glycolate, and antimony acetate; and / or,

[0052] The second catalyst is a rare earth element-containing compound, preferably at least one of lanthanum chloride, lanthanum acetylacetonate, neodymium isopropoxy, and lanthanum stearate.

[0053] In a preferred embodiment of the present invention:

[0054] In step (4):

[0055] The organic solvent is at least one selected from dichloromethane, trichloromethane, tetrahydrofuran, acetone, toluene, ethyl acetate, N,N-dimethylformamide, and dimethyl sulfoxide; and / or,

[0056] The chain extender is at least one of diisocyanates, preferably at least one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI); and / or,

[0057] The third catalyst is dibutyltin dilaurate (DBTDL).

[0058] In a preferred embodiment of the present invention:

[0059] In step (1):

[0060] The heating reaction is carried out at a temperature of 90–110°C, and / or for a reaction time of 1–3 hours; and / or,

[0061] The washing process continues until the pH value is neutral.

[0062] In a preferred embodiment of the present invention:

[0063] In step (2):

[0064] The protective gas is nitrogen, and / or the reaction temperature of the esterification reaction is 150–190°C, and / or the reaction time is 1–5 hours, and / or the esterification rate of the esterification reaction is 90–98%.

[0065] In a preferred embodiment of the present invention:

[0066] In step (3):

[0067] The pre-polymerization reaction is carried out at a temperature of 190–210°C, and / or for a reaction time of 0.5–2.5 hours, and / or under a vacuum of 600–5000 Pa; and / or,

[0068] The final polycondensation reaction is carried out at a temperature of 210–250°C, and / or for a reaction time of 0.5–4 hours, and / or with a vacuum degree of ≤300 Pa.

[0069] In a preferred embodiment of the present invention:

[0070] In step (4):

[0071] The grafting crosslinking reaction is carried out at a temperature of 40-60°C and / or for a reaction time of 1-3 hours; and / or,

[0072] The curing temperature is 20-30℃ (room temperature), and / or the curing time is 48-72h; and / or,

[0073] The drying is vacuum drying, and / or the drying temperature is 40-55°C, and / or the drying time is 48-72 hours.

[0074] The following solutions can be adopted:

[0075] (1) Preparation of hydroxymethyl modified lignin:

[0076] Lignin compounds, formaldehyde solution, and alkaline compounds are added to a hydrothermal reactor, stirred evenly, and the reactor is sealed. The temperature is then raised to 90–110°C, and the reaction time is 1–3 hours. The mixture is cooled to room temperature, washed directly with water until the pH of the solution is neutral, and finally dried to constant weight to obtain hydroxymethyl modified lignin.

[0077] (2) Preparation of furanyl polyester prepolymer:

[0078] Under a protective gas atmosphere, esterification reactions were carried out on 2,5-furandicarboxylic acid compounds, aliphatic diols, aromatic dicarboxylic acid compounds, and aliphatic dicarboxylic acids under the catalytic conditions of a first catalyst and a second catalyst to obtain the furan-based polyester prepolymer.

[0079] (3) Melt polycondensation:

[0080] When the esterification rate reaches 90-95%, the hydroxymethyl modified lignin is added to carry out pre-condensation reaction and final condensation reaction, and the pre-modified furan-based polyester material is obtained after the reaction.

[0081] (4) Grafting crosslinking:

[0082] Under a protective gas atmosphere, the pre-modified furan-based polyester material is dissolved in an organic solvent, a chain extender and a third catalyst are added, and the reaction is carried out at 40-60°C for 1-3 hours. The resulting product is cured at room temperature (20-30°C) for 48-72 hours, and then vacuum dried at 40-55°C for 48-72 hours to obtain the modified furan-based polyester material.

[0083] A third objective of this invention is to provide a lignin-modified furan-based polyester material prepared by the method described in the second objective of this invention.

[0084] The fourth objective of this invention is to provide a lignin-modified furan-based polyester material as described in the first objective of this invention, or a lignin-modified furan-based polyester material prepared by the method described in the second objective of this invention, for use as a furan-based polyester material with UV resistance properties.

[0085] This invention utilizes the characteristic that lignin reacts chemically with formaldehyde when heated under alkaline conditions, allowing hydroxymethyl groups to be introduced into the ortho position of the aromatic ring. This effectively increases the number of hydroxyl groups in lignin and the reaction sites and activity involved in polyester reactions. Simultaneously, hydroxymethylated lignin effectively reduces intermolecular forces and aggregation, resulting in good compatibility with polyesters.

[0086] This invention designs a lignin-modified furan-based polyester material using furan-based polyester and modified lignin as basic materials. Modified lignin is added as a monomer raw material to the melt polycondensation reaction of low molecular weight furan-based polyester. Then, a chain extender is added to react with the lignin-modified furan-based polyester to form urethane bonds, achieving crosslinking and reinforcement. This results in an increase in the elastic modulus, improved first-cycle recovery rate, and enhanced elastic properties of the modified furan-based polyester material. Furthermore, utilizing the inherent properties of lignin, the modified polyester material exhibits excellent UV shielding performance. This not only improves the mechanical properties of furan-based polyester materials, breaking the traditional dependence on high molecular weight polyesters, but also provides a new paradigm for the value-added utilization of lignin in sustainable bio-based polyesters. Attached Figure Description

[0087] Figure 1 The 1H NMR spectrum of the hydroxymethyl modified lignin prepared in Example 1;

[0088] Figure 2 The 1H NMR spectrum of the lignin-modified furan-based polyester material prepared in Example 1 is shown below.

[0089] Figure 3 The above is the 1H NMR spectrum of the lignin-modified furanyl polyester material prepared in Example 2.

[0090] Figure 4 The 1H NMR spectrum of the furanyl copolyester material prepared in Comparative Example 1;

[0091] Figure 5 The infrared spectrum of the lignin-modified furan-based polyester material prepared in Example 1 is shown below.

[0092] Figure 6 The image shows the UV-Vis spectrum of the lignin-modified furan-based polyester material prepared in Example 1.

[0093] Figure 7 The image shows the UV-Vis spectrum of the lignin-modified furan-based polyester material prepared in Example 2.

[0094] Figure 8 The image shows the UV-Vis spectrum of the lignin-modified furan-based polyester material prepared in Example 3.

[0095] Figure 9 The image shows the UV-Vis spectrum of the lignin-modified furan-based polyester material prepared in Example 4.

[0096] Figure 10 The UV-Vis spectrum of the furan-based copolyester material prepared in Comparative Example 1 is shown.

[0097] Figure 11 This is a comparison chart of the elastic recovery test results of the lignin-modified furan-based polyester material prepared in Example 1 and the furan-based copolyester material prepared in Comparative Example 1.

[0098] Figure 12 The diagram shows a comparison of the elastic recovery dissipation energy of the lignin-modified furan-based polyester material prepared in Example 1 and the furan-based copolyester material prepared in Comparative Example 1.

[0099] Figure 13 This is a comparison chart of the elastic recovery test results of the lignin-modified furan-based polyester material prepared in Example 2 and the furan-based copolyester material prepared in Comparative Example 3.

[0100] Figure 14This is a comparison diagram of the elastic recovery dissipation energy of the lignin-modified furan-based polyester material prepared in Example 2 and the furan-based copolyester material prepared in Comparative Example 3. Detailed Implementation

[0101] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0102] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this invention are all publicly available in the prior art and can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0103] The test methods in the embodiments and comparative examples of this invention are as follows:

[0104] GPC test: Molecular weight and its distribution were characterized using a PL-GPC220 gel permeation chromatography system from Polymer Laboratories, UK.

[0105] MRI test: 1 ¹H NMR was performed using deuterated trichloromethane (CDCl₃) as solvent, calibrated with tetramethylsilane (TMS), and quantitatively analyzed with the addition of the internal standard 1,2,4,5-tetrachlorobenzene.

[0106] The procedure was performed on a Bruker AMX300 Fourier transform NMR spectrometer at a resonance frequency of 300 MHz.

[0107] Tensile test: Tensile tests were conducted using an INSTRON-5965 tensile tester from INSTRON Corporation, USA, at a tensile rate of 50 mm / min, with each component tested 5 times.

[0108] Elastic recovery test: Tensile test was conducted using an INSTRON-5965 tensile tester from INSTRON Corporation, USA. A film with a thickness of 8-15 μm was taken and the strain was fixed at 300%. Each time, the film was stretched to 300% at a speed of 100 μm / s and then returned to the stress point of 0 at the same speed. This stretching was repeated 10 times.

[0109] Ultraviolet-visible spectrum: Tested using SHIMADZU UV-3600.

[0110]

Example 1

[0111] Preparation of hydroxymethyl modified lignin:

[0112] 10g of alkali lignin, 4.5g of 37% formaldehyde solution and 0.41g of sodium hydroxide were added to a hydrothermal reactor, stirred evenly, and the reactor was sealed. The temperature was then raised to 100℃ and the reaction time was 2h. After cooling to room temperature, the solution was washed directly with water until the pH value of the solution was neutral. Finally, it was dried to constant weight to obtain hydroxymethyl modified lignin.

[0113] Preparation of lignin-modified furan-based polyester materials:

[0114] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190℃ for esterification. When the esterification rate reached 95%, 5.5g of the above-mentioned hydroxymethyl modified lignin was added to the system for pre-condensation reaction. Vacuum reaction conditions were gradually established, the pressure was reduced to 1kPa, and the temperature was gradually increased to 210℃. After reacting for 0.5h, the final condensation reaction was carried out. The vacuum degree was controlled below 150Pa, and the reaction was carried out at 245℃ for 45min to obtain the pre-modified furan-based polyester material.

[0115] Under a protective gas atmosphere, 10 g of the pre-modified furanyl polyester material was dissolved in 80 mL of chloroform, and 0.08 g of HDI and 0.035 g of DBTDL were added. The mixture was reacted at 50 °C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27 °C for 72 hours, followed by vacuum drying at 45 °C for 48 hours to obtain the lignin-modified furanyl polyester material. The structural units derived from lignin compounds in this material comprise approximately 2 wt% of the structural units derived from furanyl polyester. The Mn content of this material is 5.3 × 10⁻⁶. 4 Mw is 10.2 × 10 4 It has a molecular weight distribution of 1.92 and a tensile modulus of 19.2 MPa.

[0116]

Example 2

[0117] Preparation of lignin-modified furan-based polyester materials:

[0118] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190°C to carry out an esterification reaction. When the esterification rate reached 95%, 13.8g of hydroxymethyl modified lignin prepared in Example 1 was added to the system to carry out a pre-condensation reaction. Vacuum reaction conditions were gradually established, the pressure was reduced to 1kPa and the temperature was gradually increased to 210°C. After reacting for 0.5h, a final condensation reaction was carried out. The vacuum degree was controlled below 150Pa and the reaction was carried out at 245°C for 45min to obtain a pre-modified furan-based polyester material. Under a protective gas atmosphere, 10 g of the pre-modified furanyl polyester material was dissolved in 80 mL of chloroform, and 0.08 g of HDI and 0.035 g of DBTDL were added. The mixture was reacted at 50 °C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27 °C for 72 hours, followed by vacuum drying at 45 °C for 48 hours to obtain the lignin-modified furanyl polyester material. The structural units derived from lignin compounds in this material comprise approximately 4.7 wt% of the structural units derived from furanyl polyester. The Mn content of this material is 5.8 × 10⁻⁶. 4 Mw is 13.4 × 10 4 It has a molecular weight distribution of 2.31 and a tensile modulus of 26.1 MPa.

[0119]

Example 3

[0120] Preparation of lignin-modified furan-based polyester materials:

[0121] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190°C to carry out an esterification reaction. When the esterification rate reached 95%, 33.2g of hydroxymethyl modified lignin prepared in Example 1 was added to the system to carry out a pre-condensation reaction. Vacuum reaction conditions were gradually established, the pressure was reduced to 1kPa and the temperature was gradually increased to 210°C. After reacting for 0.5h, a final condensation reaction was carried out. The vacuum degree was controlled below 150Pa and the reaction was carried out at 245°C for 45min to obtain a pre-modified furan-based polyester material.

[0122] Under a protective gas atmosphere, 10 g of the pre-modified furanyl polyester material was dissolved in 80 mL of chloroform, and 0.08 g of HDI and 0.035 g of DBTDL were added. The mixture was reacted at 50 °C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27 °C for 72 hours, followed by vacuum drying at 45 °C for 48 hours to obtain the lignin-modified furanyl polyester material. The structural units derived from lignin compounds in this material comprise approximately 12 wt% of the structural units derived from furanyl polyester. The Mn content of this material is 6.8 × 10⁻⁶. 4 Mw is 16.7 × 10 4 It has a molecular weight distribution of 2.44 and a tensile modulus of 29.2 MPa.

[0123]

Example 4

[0124] Preparation of lignin-modified furan-based polyester materials:

[0125] 10g of alkali lignin, 4.5g of 37% formaldehyde solution and 0.41g of sodium hydroxide were added to a hydrothermal reactor, stirred evenly, and the reactor was sealed. The temperature was then raised to 100℃ and the reaction time was 2h. After cooling to room temperature, the solution was washed directly with water until the pH value of the solution was neutral. Finally, it was dried to constant weight to obtain hydroxymethylated lignin.

[0126] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190°C to carry out an esterification reaction. When the esterification rate reached 95%, 5.5g of hydroxymethyl modified lignin prepared in Example 1 was added to the system to carry out a pre-condensation reaction. Vacuum reaction conditions were gradually established, the pressure was reduced to 1kPa and the temperature was gradually increased to 210°C. After reacting for 0.5h, a final condensation reaction was carried out. The vacuum degree was controlled below 150Pa and the reaction was carried out at 245°C for 45min to obtain a pre-modified furan-based polyester material.

[0127] Under a protective gas atmosphere, 10 g of the pre-modified furanyl polyester material was dissolved in 80 mL of chloroform, and 0.18 g of HDI and 0.045 g of DBTDL were added. The mixture was reacted at 50 °C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27 °C for 72 hours, followed by vacuum drying at 45 °C for 48 hours to obtain the lignin-modified furanyl polyester material. The structural units derived from lignin compounds in this material comprise approximately 1.5 wt% of the structural units derived from furanyl polyester. The Mn content of this material is 7.3 × 10⁻⁶. 4 Mw is 18.7 × 10 4 It has a molecular weight distribution of 2.55 and a tensile modulus of 25.2 MPa.

[0128]

Example 5

[0129] Preparation of lignin-modified furan-based polyester materials:

[0130] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190°C to carry out an esterification reaction. When the esterification rate reached 95%, 5.5g of hydroxymethyl modified lignin prepared in Example 1 was added to the system to carry out a pre-condensation reaction. Vacuum reaction conditions were gradually established, the pressure was reduced to 1kPa and the temperature was gradually increased to 210°C. After reacting for 0.5h, a final condensation reaction was carried out. The vacuum degree was controlled below 150Pa and the reaction was carried out at 245°C for 45min to obtain a pre-modified furan-based polyester material.

[0131] Under a protective gas atmosphere, 10 g of the pre-modified furan-based polyester material was dissolved in 80 mL of chloroform. 0.24 g of HDI and 0.045 g of DBTDL were added, and the mixture was reacted at 50°C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27°C for 72 hours, then vacuum dried at 45°C for 48 hours to obtain the lignin-modified furan-based polyester material. This material only partially dissolves in deuterated chloroform, with most of it only swelling, and has a tensile modulus of 49.2 MPa.

[0132] Comparative Example 1

[0133] 39 g of 2,5-furandicarboxylic acid, 41.5 g of terephthalic acid, 59 g of succinic acid, 135 g of 1,4-butanediol, 0.15 g of isopropyl titanate, 0.05 g of stannous octoate, and 0.125 g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190 °C for esterification. When the esterification rate reached 95%, vacuum reaction conditions were gradually established, and the pressure was reduced to 1 kPa. The temperature was then gradually increased to 210 °C. After reacting for 0.5 hours, polycondensation reaction was carried out at 245 °C for 45 minutes under vacuum controlled below 150 Pa, yielding a furan-based copolyester material. The Mn content of this material is 4.2 × 10⁻⁶. 4 Mw is 7.1 × 10 4 It has a molecular weight distribution of 1.69 and a tensile modulus of 12.9 MPa.

[0134] Comparative Example 2

[0135] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190℃ for esterification. When the esterification rate reached 95%, 13.8g of alkali lignin was added to the system for pre-condensation reaction. Vacuum reaction conditions were gradually established, and the pressure was reduced to 1kPa and the temperature was gradually increased to 210℃. After reacting for 0.5h, the final condensation reaction was carried out. The vacuum degree was controlled below 150Pa, and the reaction was carried out at 245℃ for 45min to obtain lignin-modified furan-based copolyester.

[0136] Under a protective gas atmosphere, 10 g of the above-mentioned lignin-modified furanyl copolyester was dissolved in 80 mL of chloroform, and 0.08 g of HDI and 0.035 g of DBTDL were added. The reaction was carried out at 50 °C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27 °C for 72 hours, and then vacuum dried at 45 °C for 48 hours to finally obtain the lignin-modified furanyl copolyester material. The Mn of this material is 4.5 × 10⁻⁶. 4 Mw is 9.4 × 10 4 It has a molecular weight distribution of 2.01 and a tensile modulus of 21.1 MPa.

[0137] Comparative Example 3

[0138] 39g of 2,5-furandicarboxylic acid, 41.5g of terephthalic acid, 59g of succinic acid, 135g of 1,4-butanediol, 0.15g of isopropyl titanate, 0.05g of stannous octoate, and 0.125g of lanthanum acetylacetonate were added to a reaction flask. Under a nitrogen atmosphere, the temperature was gradually increased to 190℃ for esterification. When the esterification rate reached 95%, a pre-condensation reaction was carried out. Vacuum reaction conditions were gradually established, and the pressure was reduced to 1kPa and the temperature was gradually increased to 210℃. After reacting for 0.5 hours, a final condensation reaction was carried out. The vacuum degree was controlled below 150Pa, and the reaction was carried out at 245℃ for 1 hour to obtain a furan-based copolyester.

[0139] Under a protective gas atmosphere, 10 g of the above-mentioned furanyl polyester was dissolved in 80 mL of chloroform, and 0.08 g of HDI and 0.035 g of DBTDL were added. The mixture was reacted at 50 °C for 1 hour. Then, 13.8 g of the hydroxymethylated lignin prepared in Example 1 was added to the system, and the mixture was reacted at 50 °C for 2 hours. The resulting product was poured into a tetrafluoroethylene mold and cured at 27 °C for 72 hours, and then vacuum dried at 45 °C for 48 hours to obtain the lignin-modified furanyl polyester material. The Mn content of this material is 4.1 × 10⁻⁶. 4 Mw is 8.4 × 10 4 It has a molecular weight distribution of 2.04 and a tensile modulus of 14.8 MPa.

[0140] The test data from the examples and comparative examples show that, with the increase of the amount of hydroxymethyl modified lignin added, under a certain proportion of chain extender, the mechanical properties and molecular weight of the modified furan-based polyester material are improved compared with those of the unmodified Comparative Example 1. A comparison between Example 2 and Comparative Example 2 shows that, at the same proportion, the addition of hydroxymethyl modified lignin results in better molecular weight and mechanical properties than unmodified alkali lignin due to the presence of more hydroxyl groups. A comparison between Example 2 and Comparative Example 3 shows that, at the same proportion, adding hydroxymethyl modified lignin in the early stages of the reaction provides more reaction sites in the system. However, adding hydroxymethyl modified lignin after the synthesis of furan-based polyester results in fewer reaction sites, only at the chain ends, which is not conducive to the introduction of hydroxymethyl modified lignin, thus leading to poorer molecular weight and mechanical properties.

[0141] Depend on Figures 11-14 It can be seen that, compared with Comparative Example 1 without the addition of hydroxymethylated lignin, the modified furan-based polyester material prepared in Example 1 of this invention has an increased elastic modulus, a significantly increased first-cycle elastic recovery rate, a corresponding decrease in dissipated energy, and a better later-cycle recovery rate than the comparative example. This indicates that the composite crosslinking structure of the material can endow the elastomer system with the ability to dissipate energy and enhance the tensile strength and toughness of the elastomer. Comparative Example 3, which synthesizes furan polyester first and then adds hydroxymethylated lignin, has lower elastic recovery performance than Example 2 of this invention, and also has higher dissipated energy. This indicates that adding hydroxymethylated lignin during the furan-based polyester prepolymer reaction process effectively increases the active sites and number of hydroxyl groups in hydroxymethylated lignin participating in the polyester reaction, resulting in more urethane bonds formed by the subsequent reaction of diisocyanate with the phenolic hydroxyl groups in the modified lignin, thereby increasing the crosslinking density and toughness of the composite material and improving its resilience and toughness.

[0142] Depend on Figures 6-10 It can be seen that, due to the basic aromatic ring skeleton of lignin and the active substituents on the aromatic ring, lignin also endows polyester elastomers with excellent UV shielding and UV resistance properties. The UV shielding effect gradually increases with the increase of hydroxymethyl modified lignin content. However, when added to a certain amount, the mechanical properties decrease to some extent because lignin is prone to agglomeration in the resin.

Claims

1. A lignin-modified furanylene polyester material, characterized in that The structural formula of the modified furan-based polyester material comprises structural units derived from a lignin-based compound and structural units derived from a furan-based polyester; The structural units derived from the lignin-based compound are 0.5wt%-12wt% of the structural units derived from the furan-based polyester, preferably 1.5wt%-12wt%.

2. A method for producing the lignin-modified furanylpolyester material according to claim 1, characterized in that The method comprises: After preparing a hydroxymethyl-modified lignin by heating a lignin-based compound and formaldehyde under alkaline conditions, the method further comprises melt polycondensation of the furan-based polyester prepolymer prepared by esterification, and graft crosslinking by a chain extender to prepare the modified furan-based polyester material.

3. The method of claim 2, wherein The method comprises: (1) Preparation of a hydroxymethyl-modified lignin: After stirring the lignin-based compound, formaldehyde solution and alkaline compound uniformly, heating reaction is performed, and the hydroxymethyl-modified lignin is prepared by washing and drying; (2) Preparation of a furan-based polyester prepolymer: Under a protective gas atmosphere, esterification is performed on 2,5-furan dicarboxylic acid-based compounds, aliphatic diols, aromatic diacid-based compounds and aliphatic diacids under catalysis of a first catalyst and a second catalyst to prepare the furan-based polyester prepolymer; (3) Melt polycondensation: The hydroxymethyl-modified lignin is added to the furan-based polyester prepolymer to perform pre-polycondensation and final polycondensation to prepare a pre-modified furan-based polyester material; (4) Graft crosslinking: The pre-modified furan-based polyester material is dissolved in an organic solvent, a chain extender and a third catalyst are added to perform graft crosslinking, and the modified furan-based polyester material is prepared after solidification and drying.

4. The method according to claim 3, wherein: In step (1): The concentration of the formaldehyde solution is 30-40%; and / or, The weight ratio of the lignin-based compound to formaldehyde is (4-10):1, preferably (5-8):1; and / or, The weight ratio of the lignin-based compound to the alkaline compound is (20-30):1, preferably (22-26):

1.

5. The method according to claim 3, wherein: In step (2): The molar ratio of the aliphatic diol to the total molar amount of the 2,5-furan dicarboxylic acid-based compound, aromatic diacid-based compound and aliphatic diacid is (1.0-4):1, preferably (1.2-2):1; and / or, The molar ratio of the aliphatic diacid to the total molar amount of the 2,5-furan dicarboxylic acid-based compound and aromatic diacid-based compound is (0.5-2):1, preferably (0.7-1.5):1; and / or, The molar ratio of the 2,5-furan dicarboxylic acid-based compound to the aromatic diacid-based compound is 1:(0.4-1.8), preferably 1:(0.4-1.2); and / or, The first catalyst is 0.05-1wt% of the aliphatic diacid, preferably 0.1-0.8wt%; and / or, The second catalyst is 0.05-2wt% of the aliphatic diacid, preferably 0.1-1wt%.

6. The method according to claim 3, wherein: In step (3): The hydroxymethyl-modified lignin is 1wt% to 25wt% of the total weight of the 2,5-furandicarboxylate compound and the aliphatic dihydric alcohol, preferably 4wt% to 15wt%.

7. The method of claim 3, wherein: In step (4): The concentration of the pre-modified furan-based polyester material after being dissolved in the organic solvent is 0.01 to 1 g / mL, preferably 0.05 to 0.5 g / mL; and / or, The chain extender is 0.2 to 2.5wt% of the weight of the pre-modified furan-based polyester material, preferably 0.3 to 2.5wt%; and / or, The third catalyst is 0.01 to 1wt% of the weight of the pre-modified furan-based polyester material, preferably 0.1 to 0.5wt%.

8. The method of claim 3, wherein: In step (1): The lignin-based compound is at least one of alkali lignin, enzymatic hydrolysis lignin, and high-boiling alcohol lignin; and / or, The basic compound is an alkali metal hydroxide, preferably sodium hydroxide and / or potassium hydroxide.

9. The method of claim 3, wherein: In step (2): The 2,5-furandicarboxylate compound is at least one of 2,5-furandicarboxylic acid, dimethyl 2,5-furandicarboxylate, and diethyl 2,5-furandicarboxylate; and / or, The aliphatic dihydric alcohol is at least one of butanediol, hexanediol, decanediol, octanediol, nonanediol, and pentanediol, preferably butanediol; and / or, The aromatic diacid-based compound is at least one of terephthalic acid, terephthalic acid ester, isophthalic acid, and isophthalic acid ester; and / or, The aliphatic diacid is at least one of adipic acid, succinic acid, sebacic acid, suberic acid, azelaic acid, brassylic acid, and glutaric acid, preferably adipic acid and / or succinic acid; and / or, The first catalyst is at least one of an organic titanium catalyst, an organic tin catalyst, and an organic antimony catalyst; preferably, the organic titanium catalyst is at least one of tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, and ethylene glycol titanate, and / or the organic tin catalyst is at least one of dibutyl tin oxide, butyl stannoic acid, dibutyl tin oxide, diethyl dibutyl tin, dioctyl tin oxide, monobutyl diisooctyl tin, and stannous octoate, and / or the organic antimony catalyst is at least one of antimony trioxide, ethylene glycol antimony, and antimony acetate; and / or, The second catalyst is a rare earth element-containing compound, preferably at least one of lanthanum chloride, lanthanum acetylacetone, neodymium isopropoxide, and lanthanum stearate.

10. The method of claim 3, wherein: In step (4): The organic solvent is at least one of dichloromethane, trichloromethane, tetrahydrofuran, acetone, toluene, ethyl acetate, N,N-dimethylformamide, and dimethyl sulfoxide; and / or, The chain extender is at least one of a diisocyanate, preferably at least one of toluene diisocyanate, isophorone diisocyanate, diphenyl methane diisocyanate, dicyclohexyl methane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; and / or, The third catalyst is dibutyltin dilaurate.

11. The method of claim 3, wherein: In step (1), The reaction temperature of the heating reaction is 90-110℃, and / or, the reaction time is 1-3h; and / or, The washing is to neutral pH.

12. The method of claim 3, wherein: In step (2), The protective gas is nitrogen, and / or, the reaction temperature of the esterification reaction is 150-190℃, and / or, the reaction time is 1-5h, and / or, the esterification rate of the esterification reaction is 90-98%.

13. The method of claim 3, wherein: In step (3), The reaction temperature of the pre-polycondensation reaction is 190-210℃, and / or, the reaction time is 0.5-2.5h, and / or, the vacuum degree is 600-5000Pa; and / or, The reaction temperature of the final polycondensation reaction is 210-250℃, and / or, the reaction time is 0.5-4h, and / or, the vacuum degree is ≤300Pa.

14. The method of claim 3, wherein: In step (4), The reaction temperature of the grafting and crosslinking reaction is 40-60℃, and / or, the reaction time is 1-3h; and / or, The curing temperature is 20-30℃, and / or, the curing time is 48-72h; and / or, The drying is vacuum drying, and / or, the drying temperature is 40-55℃, and / or, the drying time is 48-72h.

15. A lignin-modified furfuryl polyester material prepared by the method of any one of claims 2-14.

16. Use of the lignin-modified furfuryl polyester material of claim 1 or prepared by the method of any one of claims 2-14 as a furfuryl polyester material with anti-ultraviolet properties.

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